Certain types of such conveyor systems consist of a conveyor belt, a track for trolleys or some other conveyor installation by means of which work pieces are transported, for example, through a number of work stations and are subjected on their way to different operations at these stations whilst they are still being supported by the conveyor track. Such conveyor tracks are used to a considerable extent in automobile manufacture and also in the assembly and/or processing of other more complex units. However, this method requires that the operations be capable of being divided up in such a way that they need to spend more or less the same time in each of the stations, and that the stations be capable of being laid out in the sequence in which they will be transited.
In another type of conveyor system there is present a principal line, and running from it side lines which lead from the principal line to the respective work station. A conveyor system of this kind is more easily adaptable to different operating conditions than the first-mentioned system, because the work pieces can be transported from the principal line via the side lines to the work stations, where they can remain for the time necessary for the operation, whereupon they are fed back to the principal line for transport to the next station. If the principal line is executed in the form of a ring, the material can be made to cover a number of circuits, and the work stations accordingly do not need to lie in any particular sequence. Conveyor systems of this kind have been used considerably within the ready-made clothing industry. It is difficult to arrange for the different operations involved in the production of finished garments, for example sewing together, applique work, button-holing, sewing on buttons and pressing to take the same time. The production runs are also relatively short, with a constantly changing range of garments and sizes. These problems, which would very likely be insurmountable in the first-mentioned type of conveyor track, are easily overcome in the second type of conveyor system through the selective guidance of the work pieces to the different work stations, without these having to be rearranged in conjunction with a change in the production run. By using a reasonable selection of standard stations at which the various types of operations required for different types of garment can be performed, it is possible to produce a number of varying designs by guiding the material to the stations concerned in one and the same system.
The arrangement in accordance with the present invention relates in the first place to the second type of system, due to the fact that it exhibits its greatest benefits in this context. The possibility is not excluded, however, of utilizing the arrangement in conjunction with the first type of conveyor track.
An example of a conveyor system of the second type is given in U.S. Pat. No. 3,592,141, Inge Davidsson. Use is made here of an endless, loop-shaped principal conveyor and of a number of side conveyors. Trolleys carrying work pieces can be moved by the use of points and crossings from the principal conveyor to a desired side conveyor and along the latter to a stationary position at a work station. The trolley can be moved on from the work station along the side conveyor and back onto the principal conveyor for distribution to the next work station, or, after leaving the final work station, for discharging of the finished work piece. In the case of the specified system each trolley is addressed by means of a mechanism attached to it for the purpose of its distribution onto the desired side conveyor, and is then capable of being readdressed at each work station. There are other examples of similar conveyor systems in which the addressing instead takes place via a central control function.